1. Field of the Invention
The present invention is broadly concerned with an improved blank cutting machine of the type used in box making operations for the die cutting of box blanks. More particularly, it is concerned with such a machine, retrofit apparatus for existing blank cutting machines, and a corresponding method, wherein the die knife structure of the machine may be quickly and easily changed. Advantageously, an otherwise conventional blank cutting machine is equipped with changeover apparatus adjacent the rearward output of the machine which temporarily supports and permits pivoting movement of a die knife frame to an upright position facilitating knife changeover. Use of such changeover apparatus allows replacement of die knife structure in as little as two or three minutes, as compared with existing machines where such changeovers may take forty-five minutes or more.
2. Description of the Prior Art
Box making plants make use of large die cutting machines for the purpose of cutting specially configured box blanks from board stock. Generally speaking, such machines include a vertically reciprocal press member which is adapted to support a die frame, the latter carrying replaceable die knife structure having the desired box blank pattern. Incoming board stock is fed into the forward, input end of the machine and beneath the press member, whereupon the latter is lowered to cut the desired blank. The cut stock is then shifted rearwardly to the output end of the machine where it is deposited onto a conveyor or other pickup apparatus for trimming and stacking.
A significant problem with existing blank cutting machines stems from the time and effort required to change the die knife structure. In typical practice, the machine is shut down, and the die frame released from the press member and shifted rearwardly towards the output end of the machine. At this point an overhead chain hoist is employed to bodily lift the die frame from the machine and transfer it to a changeover table where the actual die changeover is accomplished. After knife replacement, the hoist must again be used to lift the die frame having the replacement die knife structure therein from the table and back into the confines of the machine. Plant workers must then guide the die frame into the machine for attachment to the press member.
This changeover procedure may often take forty-five minutes or longer to complete, and of course during all of this time the machine is inoperable. As can be appreciated, this amount of down time represents a significant loss to the plant operator. This loss is particularly acute where short box runs are made, inasmuch as the die knife structure must be changed after each short run is completed.
There is accordingly a real need in the art for an improved apparatus and method which will materially speed up the die knife changeover operation, thus reducing down time and economic loss.